About the Use of Animals for Food

Paul E. Howe.

The production of animals for human food needs to be considered from three viewpoints : Their relation to the total world food supply; the unique contributions of animal products to the health and satisfaction of man; and the direction that research should take to make the best use of the total food supply. Questions to be answered are : To what extent do animals compete with man for food? How can one make the best use of animal foods?

As the population of the world increases, man will reserve more and more of the foods, especially the cereals and grains, for his own use. He will give preference to animals that can produce and grow on foods least acceptable to him and to methods of feeding them that will contribute to the same results. The feeds allotted to animals will be those that are not acceptable to man, such as the coarser grains, roughage, and pasturage. The leafy green plants are an important part of man's dietary. There will be some competition between man and animals for the grasses. This is evident even now in the United States, where wheat and .alfalfa and other plants in the early stage of growth are commercially cut and dried, so far principally for Poultry feeding, but also packaged for human use. As a matter of fact, the product is a good vitamin supplement. Another example is the use of young green alfalfa and green grass for human food in regions of the Near East.

Byproducts from the processing of food for man are available for animal feeding. As competition increases, however, man will undoubtedly take for his own use the more important portions of what are now byproducts. This may create new problems.

Justification for the production of animals for human food lies in the unique nutritive values of their products. In addition, the inedible parts of animals are valuable because they may be converted into products useful to man.

Animal products owe their importance as food to their proteins and other essential nutrients, such as the vitamins, hormones, and calcium. Man's interest in them, however, is strongly associated with the fats the fat of meat and the cream or butter of milk. So far as we now know, everything of nutritional importance, except vitamin A, in the fats of animals can be obtained from plant fats. As a matter of fact, man obtains most of his vitamin A from the carotenoids of plants. Search should continue for evidence of the special nutritive value of fats. In general, however, animal fats serve to make animal products more palatable and to add flavor to bland vegetable foods.

The importance the average man places upon the fat of animal products has unfortunately led to failure to utilize fully the more nutritionally important parts of the animal. Thus butter commands a premium in the market, and skim milk, with its protein, calcium, riboflavin, and other important nutrients, is fed to farm animals. Often when cheese is made the whey is thrown away or fed to animals. Industry has taken steps to conserve nutrients; the whey of milk with its riboflavin is being converted into cheese and other palatable products. In the case of the meat animals and eggs, the bones and shells, sources of calcium, are discarded or made into fertilizer. Industry is making some moves to utilize the calcium of those products to increase the value of other foods. Thus, in one country, bones are finely ground and cooked with meat in canning; in another, very finely pulverized bone has been used advantageously in the manufacture of confections. In some countries the bones of small fish are an important source of calcium in the diet.

Standards of quality of the meat that is needed to supplement effectively a diet based on grains and leafy vegetables must include vitamins, in addition to other components. Fat should not be the primary criterion of quality that it tends to be today.

Strains of animals that grow rapidly, with maximum muscle development and quality and the minimum of fat, would be a reasonable goal. Quality of meat may then be an inherent characteristic of particular strains of animals and perhaps of methods of feeding, rather than degree of fatness, at present often the only measure.

All these problems are a challenge to the animal breeder and feeder. Animals and animal products will continue to contribute pleasure and profit to man and to serve as a source of nutrients. If my assumptions are correct, the experimental animal breeder and feeder must set his goal far in the future, looking toward the types of animals I have indicated and at the same time meeting immediate demands.

Meat and animal products are perishable. To assure their use as human food, the processor must study and develop ways that will preserve them and make them attractive to the consumer. The changes that occur in processing and preservation of food may affect its nutritive value and even our health. The objective of the processor, therefore, must be to retain the maximum nutritive value compatible with an acceptable product.

In most diets, animal foods are a major source of all nutrients except carbohydrates and vitamin C. The nutrients that are particularly modified in preparation of animal foods in the home and in commercial processing are the proteins, thiamine (vitamin B,), and pantothenic acid. Of these, thiamine is especially susceptible to change upon storage for long periods of time and at high temperatures. What the changes mean to an individual depends on the quantity and quality of the protein and of the vitamins in the remainder of the diet.

When the diet depends largely on the animal products for thiamine, the losses in processing and home preparation may be serious. Riboflavin is readily destroyed upon exposure to light, but it is not destroyed by heat. Milk is susceptible to loss of riboflavin on exposure to light. In the United States, milk supplies the largest proportion of riboflavin to the total daily intake; hence milk must be protected against such a loss. Vitamin A and carotene are destroyed upon exposure to oxygen. In animal foods, those vitamins are in the fat, which helps to protect them from oxidation.

The general high quality of the proteins of animal foods is an accepted fact. Heat when too high and too continuous lowers the nutritive value of protein by reducing the availability of the amino acids, especially lysine, through combinations and diminished digestibility. The best commercial processes and home cooking methods do not cause sufficient change to affect seriously the nutritive value of the usual mixed diet. Malnutrition, however, results from such practices as the steady use of a processed food of reduced nutritive value in diets on the border line of nutritional adequacy in proteins, vitamins, or minerals. In such instances, the same amount of the original food would assure at least the minimum of the nutritional value of the nutrients lost in processing.

FOOD HABITS likes and dislikes of food and prejudices for or against certain methods of preservation often interfere with our acceptance of food. Acceptance or rejection of food may act as a two-edged sword. When it is .good, it helps assure an adequate dietary; when it is harmful, it excludes necessary foods or makes us eat too much of the wrong kinds and too little of their supplements.

In the course of processing or preserving foods, there is often a loss of one or more of such important nutrients as vitamins or minerals (or even a change in the nutritive value of the proteins) that are characteristic of the unmodified food. On the other hand, some nutrients may be concentrated.

When people use processed foods in which the appearance, flavor, and attractiveness are retained but the nutrients lost, the danger is that they may not appreciate the significance of the change that has taken place. They may continue to satisfy their appetites by following their old habits, but in so doing they may fail to satisfy their requirements for specific nutrients. Unknowingly, they suffer from hidden hunger. That happened in the last war, not because the nutrients were not provided in the rations but because the soldiers neglected to eat the supplementary foods, such as lemon powder and sometimes vitamin pills, that were furnished to compensate for the losses in vitamins that had taken place in processing and storage. Too, they often failed to use all the milk products provided them because they were accustomed to drinking fresh milk and were indifferent to the canned and dried products that were available.

The Food and Nutrition Board of the National Research Council made good use of one of our food habits when it proposed the addition of vitamins and iron, valuable dietary supplements, to bread, flour, and corn meal, because everyone eats bread. The British added Calcium to their 85-percent extraction flour, partly to compensate for the phytic acid (which interferes with absorption of calcium) and partly to assure a better calcium intake.

The preference of rice-eating people for white rice, which has lost most of its thiamine, even when they know that beriberi is likely to occur, has resulted in procedures of fortifying rice that will still be white and fit the methods of preparation.

THE DANGER that malnutrition will result from the introduction of new and useful processed foods, because they may be improperly fitted into established food patterns, may be lessened in two ways.

First, the investigator and processor who develop and produce the food should make every effort to retain as much as possible of the natural nutritive value.

Second, the processor should include in his advertising program information on the composition of his product and its value in the dietary. He should also state on the label of his package the quantity of the important nutrients affected by processing that are present, or the proportion retained, as compared with that in the average natural product.

With such information, the person responsible for feeding people, whether in homes, armed forces, institutions, or public eating places, can make the correction necessary to insure the health of those for whom he is responsible. It will also make it easier for people generally to know the essentials of a good diet and to modify their food habits accordingly.

THE NEED TO RETAIN the maximum nutrients in processing is as important in animal products or byproducts intended for animal feeds as in those for -human food. State and Federal laws require statements of the composition of animal feeds on all labels. In the past, the laws have covered protein, fat, carbohydrate, fiber, and ash. With the development of the science of nutrition, they are beginning to require data on vitamins and specific minerals in feeds sold as supplements to the common feeds.